<!DOCTYPE html>
<html>
    <head lang="en">
        <meta charset="UTF-8">
        <title></title>
        <style>
        :root{/*根目录*/
            background-color: aqua
        }
        div *:not(h1){/*除h1之外的颜色*/
            color:blue;
        }
        :empty{/*没有内容的部分*/
            background-color: blueviolet
        }
        :target{/*页面跳转颜色*/
            background-color:brown;
        }
        </style>
    </head>
    <body>
        <div>
            <h2>二号标
            </h2>
            <h1>这是一个标题</h1>
            <p>这是衣蛾p表情</p>
        </div>
        <table border="1">
            <tr>
                <td></td>
                <td>ddd</td>
            </tr>
            <tr>
                <td>
                        fsdsdf
                </td>
                <td>sdfsdf</td>
            </tr>

        </table>
        <br/>
       <a href="#a1">菜单1</a>
       <a href="#a2">菜单2</a>
       <a href="#a3">菜单3</a>
       <a href="#a4">菜单4</a>
       <div id="a1">
           <h1>菜单1</h1>
           <p>菜单1内容</p>
        </div>
       <div id="a2">
            <h1>菜单1</h1>
        
            <p>菜单1内容</p>
        </div>
        <div id="a3"> 
            <h1>菜单1</h1>
            <p>菜单1内容</p>
        </div>
        <div id="a4"> 
            <h1>菜单1</h1>
            <p>菜单1内容</p>
        </div>
    </body>
</html>